The U.S. Supreme Court case Tennessee Coal, Iron & Railroad Co. et al. v. Muscoda Local No. 123 et al., in 1943, revolved around the issue of whether time spent by iron ore miners traveling to and from their work sites within mines should be considered compensable working hours under the Fair Labor Standards Act (FLSA). The plaintiffs were members of a labor union who worked for mining companies and argued that they should be paid for this travel time as it was an integral part of their job duties while underground in the mine tunnels. The defendants, several mining corporations including Tennessee Coal, Iron & Railroad Co., contended that such travel time did not constitute actual work and thus was not subject to compensation under FLSA provisions. In its decision, the Supreme Court ruled in favor of the workers stating that since these activities are necessary for productive work at these specific jobsites and require exertion on behalf of employees beyond mere physical presence; therefore they must be compensated accordingly.

In the dissenting opinion for Tennessee Coal, Iron & Railroad Co. v. Muscoda Local No. 123, Justice Frankfurter argued that the majority's decision to include travel time in underground mines as compensable work under the Fair Labor Standards Act (FLSA) was a misinterpretation of Congress' intent when passing this law. He contended that Congress intended "work" to mean physical or mental exertion controlled or required by an employer and pursued necessarily and primarily for his benefit; it did not intend to cover activities like traveling which are preliminary or postliminary actions incidental to 'work'. The justice also expressed concern about potential economic implications of such broad interpretation on industries where employees have long commutes within their workplaces but aren't engaged in productive labor during those times.